1. Field of the Invention
The present invention relates to a photosensitive drum for use in an electrophotographic image forming apparatus. The drum includes a cylindrical drum body having a photosensitive layer, a pair of flanges attached to opposed end faces of the drum body, a reinforcing stay provided inside the drum body and a drum shaft for rotatably supporting the drum body via the flange. The flanges are fixed to the reinforcing stay in such a manner that outer peripheries of the flanges are elastically contacted against the end faces of the drum body
2. Related Art
With the photosensitive drum of the above-noted type, when the pair of flanges are attached to the opposed end faces of the drum body, in order to restrict deformation in the drum body when the flanges are attached thereto and relative displacement between the axis of the drum body and the axis of the drum shaft, due to e.g. tolerances in the manufactures of the drum body, the flanges, the reinforcing stays, the flanges are fixed to the reinforcing stay in such a manner that the outer peripheries of the flanges are elastically contacted against the end faces of the drum body.
In the case of a conventional photosensitive drum illustrated in FIG. 9, a pair of bar-like support members 40 are provided integrally with a reinforcing stay 13. Each flange 12 defines through holes 41 for allowing insertion of respective ends of the bar-like support members 40. A screw 35 is threaded, from the outer side of the flange 12, on the end of the bar-like support member 40 inserted in the insertion hole 41 of each flange 12. Further, a compression spring 42 is mounted between the head of the screw 35 and the outer face of the flange 12 so as to provide an urging force for causing the outer periphery of the flange 12 to be elastically contacted against the end face of a drum body 11, whereby the flange 12 is fixed to a reinforcing stay 13.
In the photosensitive drum having the above-described construction, in causing the outer periphery of the flange to be elastically contacted against the end face of a drum body, the contact force, if excessive, will tend to invite deformation in the drum body, whereas the contact force, if insufficient, will tend to invite free rotational displacement of the flange relative to the drum body. Furthermore, non-uniformity in the contact force in the peripheral direction of the drum will tend to invite a twisting distortion in the drum body. All of these conditions tend to lead to disturbance in the formed image. For this reason, the elastic contact needs to provided so as to realize substantially uniform distribution of the appropriate amount of contact force along the peripheral direction of the drum.
However, according to the above-described conventional art, the urging force from the compression spring 42, that is, the magnitude of the contact force to be applied from the flange 12 against the drum body 11, is set by way of an amount or depth of the threading engagement of the screw 35 relative to the bar-like support member 40. Hence, in order to elastically contact the outer periphery of each flange 12 against the end face of the drum body 11 so as to realize such substantially uniform distribution of appropriate contact force along the peripheral direction of the drum, precision management of the threading depth of the screw 35 is needed and such precision management requires skill and good experience for the assembling factory worker and this also intends to invite disadvantageous increase in the manufacture cost of the drum.
The present invention has been made in view of the above-described state of the art. A primary object of this invention is to realize easier assembly of the photosensitive drum with appropriate contact force to the end face of the drum body, while restricting manufacture cost increase and avoiding need for high skill and/or experience for the factory worker who assembles the drum.